Linux: Timeouting commands in shell scripts

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Oct 122014
 

Article by Mikko Ohtamaa first posted on his blog

Often you want to automatize something using shell scripting. In a perfect world your script robot works for you without getting tired, without hick-ups, and you can just sit at the front of your desk and sip coffee.

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Then we enter the real world: Your network is disconnected. DNS goes downs. Your HTTP hooks and downloads stall. Interprocess communication hangs. Effectively this means that even if your script is running correctly from the point of operating system it won’t finish its work before you finish your cup of coffee.

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How to check if you are vulnerable to shellshock

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Sep 292014
 

The most new and dangerous bug around it’s the one called “shellshock”, this is a security bug in the widely used Unix Bash shell which was disclosed on 24 September 2014. Many Internet daemons, such as web servers, use Bash to process certain commands, allowing an attacker to cause vulnerable versions of Bash to execute arbitrary commands. This can allow an attacker to gain unauthorized access to a computer system.

The bug causes Bash to unintentionally execute commands when they are stored in specially crafted environment variables. Within days, a series of further related vulnerabilities in Bash were found, leading to the need for further patches.

By 25 September, botnets based on computers compromised with this exploit were being used by attackers for distributed denial-of-service attacks and vulnerability scanning, source wikipedia

Let’s see how to check if your computer or server is vulnerable.
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How to change an user password in Linux

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Aug 292014
 

If you manage a server with many different users or just your family computer you will probably have many different accounts to manage, and one important aspect of any account it’s its password.

In this small article I’ll show you how to use the basic passwd command but also how to do some small bash script or use a web application, if you have a more complex environment, such as a central ldap server that keep all your accounts information.
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Counting and listing hard links on Linux

Article by giannis_tsakiris first posted on http://www.giannistsakiris.com A hard link is actually nothing more than a regular directory entry, which in turn can be seen as a pointer to the actual file’s data on the disk. The cool thing about hard-links is that a file can be stored once on the disk, and be linked to multiple times, […]

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Linux Terminal: the tee command

The command “tee” it’s one of the basic commands that you should find in any system, yet it’s not so popular or use, this command reads standard input and writes it to both standard output and one or more files, effectively duplicating its input. It is primarily used in conjunction with pipes and filters. The […]

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